Fifty-four people died of heroin overdoses last year in Hennepin County — slightly more than one every week of the year — in the deadliest year on record for such deaths.

The grim tally was nearly seven times higher than just three years earlier, when eight people died, the Hennepin County Sheriff's Office said Tuesday.

"HCSO investigators have found heroin sales and users in suburban, rural and urban areas of our county," Sheriff Rich Stanek said.

The overdoses here and nationwide have been blamed on a surge of cheap heroin and widespread addictions to prescription opiate drugs like OxyContin and Vicodin. A common path to heroin overdoses begins with addiction to painkillers that were originally prescribed for a legitimate medical need, experts say.

A Minnesota Drug Abuse Trends report released last month found signs that overdose deaths were climbing in Hennepin County, with a surge of 69 heroin and prescription painkiller deaths in the first half of the year. That compared to 84 such deaths in all of 2012.

About half of those overdose deaths in Hennepin County occurred among people in their 20s, said Carol Falkowski, the founder of Drug Abuse Dialogues and the author of the Drug Trends report.

Heroin's dark history made headlines this week with the news that Oscar-winning actor Philip Seymour Hoffman was found dead over the weekend in his apartment, with a syringe stuck in his arm. His death has not officially been blamed on heroin, but police reported finding dozens of bags of the drug in his room.

Matt McKinney • 612-217-1747